The proposed work is to study genetic and physiological factors that control the expression of immunoglobulins. We will examine the basis for expression and dominance of a particular idiotype in the anti-rho-azophenlarsonate response of A/J mice. We will examine the number and sequence of structural genes encoding the dominant idiotype and compare them to the genes encoding a recently discovered, non-dominating idiotype. The genetic constitution of strains of mice not-expressing these idiotypes will be examined. Nucleic acid probes encoding the heavy chain variable regions of each idiotype will be prepared from hybridomas expressing the corresponding idiotype. The relative precursor frequency of B cells corresponding to each idiotype will also be examined. The major idiotype (CRI) has been found to be composed of many individual sequences. We will examine regulatory T cells that control the CRI to determine if the collection of idiotype bearing sequences is regulated as a family or as individual antibodies. This will be done by using individual hybridoma proteins and cloned regulatory T cell lines.